• An ongoing document review in a case involving President Donald Trump's ex-lawyer Michael Cohen cost more than $330,000 in May.
  • Special master Barbara Jones is charging $700 an hour to screen materials seized from Cohen by the FBI.
  • Cohen is being eyed by prosecutors for, among other things, a hush money payment to porn star Stormy Daniels.
President Donald Trump's lawyer Michael Cohen leaves his hotel in New York, June 15, 2018.

A federal judge Thursday approved a $338,421 invoice from a "special master" for 31 days of work last month reviewing materials seized from President Donald Trump's ex-lawyer, Michael Cohen.

Barbara Jones, a former federal judge, is charging $700 an hour to screen the thousands of files taken in federal raids from Cohen for potential withholding from prosecutors because of attorney-client privilege protection.

Jones' prior invoice for work done from April 24 to 30, had totaled $47,390. As with that bill, Jones' most recent set of charges submitted to Judge Kimba Wood was not contested by federal prosecutors or Cohen, as well as by the president or the Trump Organization. Wood approved payment of the invoice from Jones.

Trump and his company have intervened in the case, claiming that many of the documents could relate to them.

Prosecutors are paying half of Jones' costs. The remaining share is being paid by Cohen, the president and the Trump Organization.

Cohen, 51, has not been charged, but currently is the target of a criminal investigation by federal prosecutors in New York City. He is being eyed for his business dealings and for a $130,000 payment to porn star Stormy Daniels who alleges she had an affair with Trump. The White House has denied the president had sex with Daniels.

Jones to date has found that just a tiny fraction of items — fewer than 200 out of more than 292,000 — are exempt from disclosure to prosecutors in the case because of attorney-client privilege.